The use of mobile communications networks has increased over the last decade. Operators of mobile communications networks have increased the number of base stations in order to meet an increased demand for service by users of mobile communications networks. The operators of mobile communications networks wish to reduce the running costs of respective base stations. One option to do this is to implement a radio system as an antenna-embedded radio forming an active antenna array. Many of the components of the antenna-embedded radio may be implemented on one or more chips.
Distributed antenna systems are known in the art. The distributed antenna system often employs single antenna elements to provide mobile communications systems throughout the indoor of buildings and also across campus-style environments. These distributed antenna systems are dynamic and can be quickly reconfigured to cope with changing mobile telecommunications traffic.
One example of such a distributed antenna system has been developed by Kathrein-Werke K G, Rosenheim, Germany and is marketed under the name “K-BOW”. This system aggregates data traffic with a centralised platform and transmits multiple combinations of telecommunications signals to individual radio units (RUs) for transmission by individual radio units or single antenna elements. The system is remotely controlled using a network monitoring system, so that capacity in any area within the building or over the campus can be dynamically increased or decreased. The system uses a broadband amplifier in the individual radio units. The single antenna elements are able to broadcast signals using a plurality of frequencies.
US Patent U.S. Pat. No. 5,223,848 teaches an antenna comprising at least one pair of radiator elements with orthogonal linear polarisation. One of the radiator elements is fed with a signal with a phase difference of 90° relative to the signal fed to the other radiator element. Each of the radiator elements transmits and/or receives signals at two different frequencies having orthogonal polarisations. One of the radiator elements operates at a first frequency with a horizontal polarisation and a second frequency with a horizontal polarisation. The other radiator element operates at the first frequency with a horizontal polarisation and at the second frequency with a vertical polarisation.
Japanese Patent JP 4682979 B2 teaches an antenna, which is capable of duplexing cross-polarisation communication. Four antennas serving two frequencies are arranged in four sections with opposite orthogonal polarisation.